The present invention relates to a variable pitch propeller for a watercraft, in which the main shaft of the motor located in the hull of the watercraft is coupled directly or via a gear to the propeller drive shaft, which extends through the hull wall, said propeller shaft is supported by a bearing located in a hollow brace strut, outside the hull. The brace strut is fixed to the hull wall and is located nearby the variable pitch propeller, the latter being equipped with adjustable blades mounted in the propeller hub. A connecting rod linkage is provided for adjusting the propeller blades, whose connecting rods are displaceable by means of a rotary slide coupling through an adjusting linkage, actuated by a linear motor (electric or hydraulic) and controlled manually or electronically.
Various constructions of variable pitch propellers and their adjustment means enabling the pitch of the propeller blades to be adjusted are known. They serve, on the one hand, to better utilize the installed power of the motor in a watercraft and, on the other, to facilitate the handling of said watercraft. The pitch of the propeller blades can be adapted manually or automatically to the particular use, it being possible to adjust the propeller blades for reverse thrust.
Whereas the variable pitch propeller is driven by a propeller shaft driven by a motor drive in the interior of the watercraft, the adjustment of the propeller blades is brought about in different ways. Thus it is known to introduce a pressure medium into the propeller hub and thereby act on a piston system arranged in the hub enabling the propeller blades to be adjusted (U.S. Pat. No. 2,931,443).
It is also known to adjust the propeller blades by means of a mechanical linkage or gear, the adjusting force being applied manually. The adjusting movement is transferred by means of a rotary slide coupling mounted in the propeller hub to connecting rods enabling the individual propeller blades to be adjusted (U.S. Pat. No. 2,742,097). The rotary slide coupling comprises a non-rotary part and a rotary part, between which are installed radial and axial bearings, which, on the one hand, permit the relative movement of the two parts and, on the other, transfer the adjusting force from the non-rotary to the rotary part.
Two constructional embodiments are known for the arrangement of the variable pitch propeller on the watercraft. In the first construction, known as the stern drive, the hub is incorporated into part of the rudder body and is driven by means of two mitre gears, through which a Z-shaped arrangement of the shaft from the drive motor to the adjusting hub is obtained.
In another construction, the motor shaft is coupled directly or via a gear to the propeller shaft, which extends outwards through the watercraft hull and carries at its end the variable pitch propeller. The main bearing is supported on the watercraft hull by means of a support body, which is also called a propeller bracket or brace strut.